Newby Newb. Can you mix 12v and 24v panels into a 12v PMW charge controller?

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Bass-O-Matic
Bass-O-Matic Registered Users Posts: 45 ✭✭
in Caravan, Recreational Vehicle, and Marine Power Systems #1
I want to setup a 400watt solar system for my RV. All my appliances are 12v. I made the newb mistake of buying stuff first so I have two 85watt poly solar panels.... and a 12v charge controller.  Sunforce 60032 30 Amp Digital Charge Controller
I think made a mistake... I now see 12v / 24v charge controllers... auto switching.

1.Does that mean I can mix and match 12v and 24v panels ? 

2. What is the biggest 12v panel out there? I found a 100 watt panel. If I found a bigger one I wouldn't have to buy a new controller.

Thanks
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  • oil pan 4
    oil pan 4 Solar Expert Posts: 767 ✭✭✭✭
    #2
    The biggest "12 volt panels" I have seen were over 300 watts.
    The panel voltage going into the controller needs to be the same.
    Why do you think you need to buy another charge controller?

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

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  • Bass-O-Matic
    Bass-O-Matic Registered Users Posts: 45 ✭✭
    #3
    Oh, only if I was going to mix and match which sounds like a non starter. Where do I buy these big panels? Thanks
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  • oil pan 4
    oil pan 4 Solar Expert Posts: 767 ✭✭✭✭
    #4
    One from here, its 285 watt and its voltage is a bit higher than normal for a "12 volt panel" but it will work very well with a real MPPT charge controller.
    http://www.solar-electric.com/solarworld-sunmodule-sw285-monocrystalline-solar-panel-33mm.html

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #5
    I believe the 12v / 24v reference is battery voltage. So if you have a 12V battery bank you get 12V panels (18+ VOC) in order to charge them. Something like 4 100 watt panels in parallel would be a good example. That would charge a 160 to 230AH battery bank at 12 volts.   
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #6
    Raj174 said:
    So if you have a 12V battery bank you get 12V panels (18+ VOC) in order to charge them.   
    18+ volts is the Vmp (not Voc) of a 12 volt panel.  --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • Photowhit
    Photowhit Solar Expert Posts: 6,017 ✭✭✭✭✭
    edited June 2016 #7

    Mixing might work, but only at the loss of much of the '24 volt' panels potential energy.

    I know evergreen made some 200 watt 12 volt panels, not sure what the largest is currently.

    Not sure why you think "...If I found a bigger one I wouldn't have to buy a new controller" You will be limited by the 30 amp capacity of your charge controller. You could have enough panels in parallel to reach that capacity, if they are 30 watt or 300 watt.

    The pair of these 165watt panels with your 85 watt panels would max out your charge controller.

    https://www.amazon.com/Solar-Panel-Charging-Battery-Efficiency/dp/B00G2IZ1VW/ref=sr_1_1?ie=UTF8&qid=1466769637&sr=8-1&keywords=165+watt+solar 

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #8
    Thanks for the correction vtmaps
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • papab
    papab Registered Users Posts: 67 ✭✭
    #9
    oil pan 4 said:
    One from here, its 285 watt and its voltage is a bit higher than normal for a "12 volt panel" but it will work very well with a real MPPT charge controller.
    http://www.solar-electric.com/solarworld-sunmodule-sw285-monocrystalline-solar-panel-33mm.html
    that's a24 v panel
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    edited June 2016 #10
    That's actually a 60 cell grid-tie panel, which is 30V. A standard 24V panel will have 72 cells (Vmp~36 volts).

    [fix typo. -Bill B.]
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • papab
    papab Registered Users Posts: 67 ✭✭
    #11
    ?? Vmp is 31.3?
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  • papab
    papab Registered Users Posts: 67 ✭✭
    #12
    Sorry, I guess that is less than typical for a 24V panel.

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,693 admin
    #13
    A 60 cell silicon panel will have Vmp~30 volts (1/2 volt per cell). I think Raj174 has a typo (20 volts)--I will fix to prevent confusion.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Bass-O-Matic
    Bass-O-Matic Registered Users Posts: 45 ✭✭
    #14
    Thanks again! I think I'll just max out my controller and leave it at that. Dry ice is pretty amazing stuff.
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #15
    Sorry Bill, I was inferring 20V nominal for 60 cells. Just as 24V is nominal for 72 cells. 
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • oil pan 4
    oil pan 4 Solar Expert Posts: 767 ✭✭✭✭
    edited June 2016 #16
    papab said:
    oil pan 4 said:
    One from here, its 285 watt and its voltage is a bit higher than normal for a "12 volt panel" but it will work very well with a real MPPT charge controller.
    http://www.solar-electric.com/solarworld-sunmodule-sw285-monocrystalline-solar-panel-33mm.html
    that's a24 v panel
    Typical 24 panel open current voltage is 40 up to 44 volts.
    A 30 volt panel is an ok choice for a 12v system with real MPPT controller, but its more likely intended for a grid tie setup, series 3 of them up for around 90v and you are good to go.
    It would work for a 24v system if you have a good MPPT controller.
    A good MPPT controller wont see any noticeable efficiency drop charging a 12v system with a 60 cell panel. If you used a PWM charge controller, that would be a horrible setup. With a PWM controller it would only be like 40 or 50% efficient.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,693 admin
    #17
    Raj, Oh, you where estimating it as a "20 volt" battery bank... A "different" way of answering the question.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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